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What we see from the Earth's surface with our eyes are just stars, any planets surrounding them - indeed, entire planetary systems are not visible by the naked eye. That does not mean that there aren't any planets around those stars, the exoplanets listed in this European based Exoplanet catalogue were detected using much more precise and sophisticated ...

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Types of observations (at least): Lyman $\alpha$ forest at $z\approx 2.5-6.5$ Thomson Scattering Optical depth for Cosmic Microwave Background radiation Intergalactic Medium temperature at $z<\approx 6$ Lyman $\alpha$: One method: An absorption phenomenon seen in the spectra of background quasi-stellar objects. Based on the neutral hydrogen ...

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A top's precession is caused by torque from the point not being aligned with the center of gravity, this tends to try to get the top to rotate away from the stable axis. In the case of Earth, the oblateness interacts with the sun's, moon's, and Jupiter's gravity to try to align the axis of rotation perpendicular to orbital plane. This is a torque that tries ...

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